Electroactive materials for metal-ion batteries

Abstract

This invention relates to particulate electroactive materials consisting of a plurality of composite particles, wherein the composite particles comprise a plurality of silicon nanoparticles dispersed within a conductive carbon matrix. The particulate material comprises 40 to 65 wt % silicon, at least 6 wt % and less than 20% oxygen, and has a weight ratio of the total amount of oxygen and nitrogen to silicon in the range of from 0.1 to 0.45 and a weight ratio of carbon to silicon in the range of from 0.1 to 1. The particulate electroactive materials are useful as an active component of an anode in a metal ion battery.

The invention claimed is: 
     
       1. Composite particles comprising silicon nanoparticles dispersed within a conductive carbon matrix, wherein the composite particles:
 (i) have a D 50  particle diameter of no more than 25 μm, 
 (ii) have a particle size distribution span ((D 90 -D 10 )/D 50 ) of 5 or less, 
 (iii) have a weight ratio of a total amount of oxygen and nitrogen to silicon of no more than 0.42, 
 (iv) have a weight ratio of carbon to silicon of at least 0.2, 
 (v) comprise less than 18 wt % oxygen, and 
 (vi) comprise pores having a diameter of less than 2 nm distributed throughout their volume. 
 
     
     
       2. The composite particles according to  claim 1 , wherein the silicon nanoparticles comprise a nanoparticle core and a nanoparticle surface, wherein the nanoparticle surface comprises a compound of oxygen or a compound of nitrogen or a mixture thereof. 
     
     
       3. The composite particles according to  claim 1 , wherein the composite particles comprise 40 to 65 wt % silicon. 
     
     
       4. The composite particles according to  claim 1 , wherein the composite particles have a D 99  particle diameter of no more than 50 μm. 
     
     
       5. The composite particles according to  claim 1 , wherein the silicon nanoparticles have a D 50  particle diameter of no more than 120 nm. 
     
     
       6. The composite particles according to  claim 1 , wherein the surface of the silicon nanoparticles comprises silicon oxide. 
     
     
       7. The composite particles according to  claim 1 , wherein the composite particles have an intra-particle porosity of no more than 30%, as determined by mercury porosimetry. 
     
     
       8. The composite particles according to  claim 1 , wherein the composite particles have a BET surface area of no more than 100 m 2/ g. 
     
     
       9. The composite particles according to  claim 1 , wherein the composite particles have a BET surface area of no more than 30 m 2/ g. 
     
     
       10. The composite particles according to  claim 9 , wherein the composite particles comprise a carbon coating. 
     
     
       11. The composite particles according to  claim 1 , wherein the composite particles have a specific charge capacity on first lithiation of at least 1200 mAh/g. 
     
     
       12. The composite particles according to  claim 1 , comprising from 0.1 to 8 wt % of one or more elements selected from aluminum, iron, copper, gallium, magnesium, calcium, titanium and zirconium with balance of the material being silicon, carbon, nitrogen, and oxygen. 
     
     
       13. The composite particles according to  claim 1 , wherein the particulate material comprises at least 80 wt % in total of silicon, carbon, oxygen and nitrogen. 
     
     
       14. The composite particles according to  claim 13 , wherein the composite particles comprise at least 98 wt % in total of silicon, carbon, oxygen, and nitrogen. 
     
     
       15. The composite particles according to  claim 1 , wherein the conductive carbon matrix has an amorphous structure with graphite-like character. 
     
     
       16. The composite particles according to  claim 1 , wherein the conductive carbon matrix has been obtained by pyrolysis of a pyrolytic carbon precursor. 
     
     
       17. The composite particles according to  claim 1 , comprising cross-links between the silicon nanoparticles and the conductive carbon matrix. 
     
     
       18. The composite particles according to  claim 1 , wherein the composite particles comprise a carbon coating. 
     
     
       19. The composite particles according to  claim 18 , wherein the carbon coating has been obtained by a chemical vapor deposition (CVD) method. 
     
     
       20. The composite particles according to  claim 1 , wherein the composite particles have been subjected to a size reduction step. 
     
     
       21. The composite particles according to  claim 20 , wherein the size reduction step comprises ball milling, planetary milling, jet milling or a combination thereof. 
     
     
       22. The composite particles according to  claim 20 , wherein the composite particles comprise a carbon coating. 
     
     
       23. An electrode comprising an electrode composition forming a layer on a current collector, the electrode composition comprising the composite particles according to  claim 1  and at least one other component selected from: (i) a binder; (ii) a conductive additive; and (iii) an additional particulate electroactive material. 
     
     
       24. The electrode according to  claim 23 , wherein the composite particles constitute from 0.5 to 80 wt % of total dry weight of the electrode composition. 
     
     
       25. A rechargeable metal-ion battery comprising an anode, wherein the anode comprises the composite particles according to  claim 1 .